As far as I see, the problem is that datatable, tree and autocomplete use the fa-circle-o-notch icon from Font Awesome by default, which does not exist in Material Icons. So you need to replace this with an existing icon like ui-icon-replay with the setting loadingIcon. The other problem is that the classes fa-spin and fa-2x defined by Font Awesome also do not exist in Ultima, but they are used by PrimeNG. So you need to copy them over to Ultima, in order to show the icon spinning and enlarged.

I'm going to post a solution for you that you're free to use if you'd like. I personally like the splash screen loading bar so I devised a way to use that for loading.

First thing is assuming you're using 4.3.0 with the latest CSS. lf you're using an older version this might be easier as I've used this for a while and it took slight more modification on 4.3.0. Either way you'll need to do a few slight modifications to _splash.scss. You will need to remove width: 100%; & position: fixed; from the .splash-screen. (you'll need to revisit this in the index.html. I have this explained below as well) Then remove margin-top:20px from .load-bar. Since you're removing 20px from the load bar you'll need to add padding-bottom: 20px to the .logo. Those are all you need to do to have the splash screen work and display above the datatable during loading. Below is my splash but I have additional changes as my logo is a different size than Ultima and I also changed the colors to reflect the blue-grey theme colors